AstroPixel Processor and bad pixels problem

[pmrid (Peter)]

Here is a crop from an stacked image. You will see immediately the repeated pattern of red, green, blue color blocks - identical blocks.

These will almost certainly be the product of dithering and something I would expect Sigma Clipping would pick up and remove. But in APP, this is not happening and so far, I haven't found a reason/solution.

Stacking in DSS does the job nicely but not APP.

Anyone??

[Geochron (Jon)]

Hi Peter,

I have never seen anything like this and I use APP for all my stacking, without any dramas. Happy to compare stacking parameters if you wish - do you use the default values?

cheers, Jon

[Dave882 (David)]

Hi mate I was getting this as well. Same with you it just started for no particular reason a while back and I suspect there may have been a change in the app stacking / calibration algorithms on one of the updates. It is caused by hot or warm pixels on your sensor. It can be reduced by adjusting the diff reaction protection, but the only way I could properly fix this was to use dark calibration frames. That solved it for me and I’m confident you’ll find the same.

[pmrid (Peter)]

Originally Posted by Dave882

Hi mate I was getting this as well. Same with you it just started for no particular reason a while back and I suspect there may have been a change in the app stacking / calibration algorithms on one of the updates. It is caused by hot or warm pixels on your sensor. It can be reduced by adjusting the diff reaction protection, but the only way I could properly fix this was to use dark calibration frames. That solved it for me and I’m confident you’ll find the same.

Hi David, thanks but unfortunately, these images were stacked with darks. I haven't been using flats but I doubt that would make a difference.

The problem seems to be in the way hotvand cold pixels are managed in the stacking process. I just can't yet figure out how these things are managed in APP.

[Dave882 (David)]

Originally Posted by pmrid

Hi David, thanks but unfortunately, these images were stacked with darks. I haven't been using flats but I doubt that would make a difference.

The problem seems to be in the way hotvand cold pixels are managed in the stacking process. I just can't yet figure out how these things are managed in APP.

Hmm interesting. How old are you darks / bias frames? Perhaps in need of updating?

[Nikolas (Nik)]

Try these settings

[Startrek (Martin)]

In regards to cooled CMOS cameras, Hot , Cold and Uneven pixels are only completely removed in the stacking process if you calibrate your data correctly with the full Calibration Suite , irrespective of the type of stacking software you use ( DSS included)

Darks to calibrate your Lights ( same Temperature, Gain and Exposure )
Flat Darks ( not Bias ) to calibrate your Flats ( same Temperature, Gain and Exposure )
Bias will calibrate your Flats but not on every camera ( Flat Darks are the Gold Standard ) I shifted from Bias to Flat Darks 6 months ago even though Bias worked ok with my ZWO 2600MC and ZWO 2600MM.

A lot of folk don’t use Flats but again ask any stacking software developer or advanced astrophotographer and they will agree that indeed they improve your images.

I totally concur

Cheers
Martin

[pmrid (Peter)]

Originally Posted by Nikolas

Try these settings

Thank you Nik. I just did that on a stack of OSC subs on Barnards Galaxy taken last night.
Here's a )[highly compressed] image.

Taken with a ZWO107FF quad, an ASI585MC Pro cam, An Optalong UV/IR Cut filter over a 4 hours stretch (48x300scs).

Happily I cannot detect any sign of those bad pixels.

Thank you.